Ross Tetjana

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Ross
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Tetjana
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  • Preprint
    Laboratory observations of double-diffusive convection using high-frequency broadband acoustics
    ( 2008-09) Ross, Tetjana ; Lavery, Andone C.
    High-frequency broadband (200-300 kHz) acoustic scattering techniques have been used to observe the diffusive regime of double-diffusive convection in the laboratory. Pulse compression signal processing techniques allow 1) centimetre-scale interface thickness to be rapidly, remotely, and continuously measured, 2) the evolution, and ultimate merging, of multiple interfaces to be observed at high-resolution, and 3) convection cells within the surrounding mixed layers to be observed. The acoustically measured interface thickness, combined with knowledge of the slowly-varying temperatures within the surrounding layers, in turn allows the direct estimation of double-diffusive heat and buoyancy fluxes. The acoustically derived interface thickness, interfacial fluxes and migration rates are shown to support established theory. Acoustic techniques complement traditional laboratory sampling methods and provide enhanced capabilities for observing the diffusive regime of double-diffusion in the ocean.
  • Article
    Acoustic detection of oceanic double-diffusive convection : a feasibility study
    (American Meteorological Society, 2010-03) Ross, Tetjana ; Lavery, Andone C.
    The feasibility of using high-frequency acoustic scattering techniques to map the extent and evolution of the diffusive regime of double-diffusive convection in the ocean is explored. A scattering model developed to describe acoustic scattering from double-diffusive interfaces in the laboratory, which accounted for much of the measured scattering in the frequency range from 200 to 600 kHz, is used in conjunction with published in situ observations of diffusive-convection interfaces to make predictions of acoustic scattering from oceanic double-diffusive interfaces. Detectable levels of acoustic scattering are predicted for a range of different locations in the world’s oceans. To corroborate these results, thin acoustic layers detected near the western Antarctic Peninsula using a multifrequency acoustic backscattering system are shown to be consistent with scattering from diffusive-convection interfaces.
  • Article
    Acoustic scattering from density and sound speed gradients : modeling of oceanic pycnoclines
    (Acoustical Society of America, 2011-12-20) Ross, Tetjana ; Lavery, Andone C.
    A weak-scattering model that allows prediction of acoustic scattering from oceanic pycnoclines (and the accompanying sound speed gradients) based on hydrographic profiles is described. Model predictions, based on profiles from four locations, indicate that scattering from oceanic pycnoclines is measurable using standard scientific sonars operating at frequencies up to 200 kHz but generally only for pycnocline thicknesses less than 10 m. Accurate scattering models are key to assessing whether acoustic remote sensing can be used to map oceanic pycnoclines and for determining whether scattering from pycnoclines needs to be taken into account when estimating, for instance, zooplankton abundance from acoustic data.
  • Article
    Toward quantifying the increasing role oceanic heat in sea ice loss in the new Arctic
    (American Meteorological Society, 2015-12) Carmack, Eddy C. ; Polyakov, Igor V. ; Padman, Laurie ; Fer, Ilker ; Hunke, Elizabeth C. ; Hutchings, Jennifer K. ; Jackson, Jennifer M. ; Kelley, Daniel E. ; Kwok, Ron ; Layton, Chantelle ; Melling, Humfrey ; Perovich, Donald K. ; Persson, Ola ; Ruddick, Barry R. ; Timmermans, Mary-Louise ; Toole, John M. ; Ross, Tetjana ; Vavrus, Steve ; Winsor, Peter
    The loss of Arctic sea ice has emerged as a leading signal of global warming. This, together with acknowledged impacts on other components of the Earth system, has led to the term “the new Arctic.” Global coupled climate models predict that ice loss will continue through the twenty-first century, with implications for governance, economics, security, and global weather. A wide range in model projections reflects the complex, highly coupled interactions between the polar atmosphere, ocean, and cryosphere, including teleconnections to lower latitudes. This paper summarizes our present understanding of how heat reaches the ice base from the original sources—inflows of Atlantic and Pacific Water, river discharge, and summer sensible heat and shortwave radiative fluxes at the ocean/ice surface—and speculates on how such processes may change in the new Arctic. The complexity of the coupled Arctic system, and the logistic and technological challenges of working in the Arctic Ocean, require a coordinated interdisciplinary and international program that will not only improve understanding of this critical component of global climate but will also provide opportunities to develop human resources with the skills required to tackle related problems in complex climate systems. We propose a research strategy with components that include 1) improved mapping of the upper- and middepth Arctic Ocean, 2) enhanced quantification of important process, 3) expanded long-term monitoring at key heat-flux locations, and 4) development of numerical capabilities that focus on parameterization of heat-flux mechanisms and their interactions.
  • Article
    Acoustic scattering from double-diffusive microstructure
    (Acoustical Society of America, 2007-09) Lavery, Andone C. ; Ross, Tetjana
    Laboratory measurements of high-frequency broadband acoustic backscattering (200–600 kHz) from the diffusive regime of double-diffusive microstructure have been performed. This type of microstructure, which was characterized using direct microstructure and optical shadowgraph techniques, is identified by sharp density and sound speed interfaces separating well-mixed layers. Vertical acoustic backscattering measurements were performed for a range of physical parameters controlling the double-diffusive microstructure. The echoes have been analyzed in both the frequency domain, providing information on the spectral response of the scattering, and in the time domain, using pulse compression techniques. High levels of variability were observed, associated with interface oscillations and turbulent plumes, with many echoes showing significant spectral structure. Acoustic estimates of interface thickness (1–3 cm), obtained for the echoes with exactly two peaks in the compressed pulse output, were in good agreement with estimates based on direct microstructure and optical shadowgraph measurements. Predictions based on a one-dimensional weak-scattering model that includes the actual density and sound speed profiles agree reasonably with the measured scattering. A remote-sensing tool for mapping oceanic microstructure, such as high-frequency broadband acoustic scattering, could lead to a better understanding of the extent and evolution of double-diffusive layering, and to the importance of double diffusion to oceanic mixing.
  • Article
    On the turbulent co-spectrum of two scalars and its effect on acoustic scattering from oceanic turbulence
    (Cambridge University Press, 2004-08-24) Ross, Tetjana ; Garrett, Christopher ; Lueck, Rolf
    While acoustic scatter from oceanic turbulence is sensitive to temperature–salinity covariations, there are unfortunately no published measurements of the turbulent temperature–salinity co-spectrum. Several models have been proposed for the form of the co-spectrum of two scalars in turbulence, but they all produce unsatisfactory results when applied to the turbulent scattering equations (either predicting negative scattering cross-sections in some regimes or predicting implausible levels of correlation between temperature and salinity at some scales). A new model is proposed and shown to give physically plausible scattering predictions in all density regimes. High-frequency acoustic data illustrate the importance of the co-spectrum for acoustic scattering, but were collected in a density regime where there is little difference between the co-spectrum models.
  • Article
    Anisotropy in high-frequency broadband acoustic backscattering in the presence of turbulent microstructure and zooplankton
    (Acoustical Society of America, 2012-08) Leong, Doris ; Ross, Tetjana ; Lavery, Andone C.
    High-frequency broadband (120–600 kHz) acoustic backscattering measurements have been made in the vicinity of energetic internal waves. The transducers on the backscattering system could be adjusted so as to insonify the water-column either vertically or horizontally. The broadband capabilities of the system allowed spectral classification of the backscattering. The distribution of spectral shapes is significantly different for scattering measurements made with the transducers oriented horizontally versus vertically, indicating that scattering anisotropy is present. However, the scattering anisotropy could not be unequivocally explained by either turbulent microstructure or zooplankton, the two primary sources of scattering expected in internal waves. Daytime net samples indicate a predominance of short-aspect-ratio zooplankton. Using zooplankton acoustic scattering models, a preferential orientation of the observed zooplankton cannot explain the measured anisotropy. Yet model predictions of scattering from anisotropic turbulent microstructure, with inputs from coincident microstructure measurements, were not consistent with the observations. Possible explanations include bandwidth limitations that result in many spectra that cannot be unambiguously attributed to turbulence or zooplankton based on spectral shape. Extending the acoustic bandwidth to cover the range from 50 kHz to 2 MHz could help improve identification of the dominant sources of backscattering anisotropy.
  • Article
    Argo data 1999-2019: two million temperature-salinity profiles and subsurface velocity observations from a global array of profiling floats.
    (Frontiers Media, 2020-09-15) Wong, Annie P. S. ; Wijffels, Susan E. ; Riser, Stephen C. ; Pouliquen, Sylvie ; Hosoda, Shigeki ; Roemmich, Dean ; Gilson, John ; Johnson, Gregory C. ; Martini, Kim I. ; Murphy, David J. ; Scanderbeg, Megan ; Udaya Bhaskar, T. V. S. ; Buck, Justin J. H. ; Merceur, Frederic ; Carval, Thierry ; Maze, Guillaume ; Cabanes, Cécile ; André, Xavier ; Poffa, Noé ; Yashayaev, Igor ; Barker, Paul M. ; Guinehut, Stéphanie ; Belbeoch, Mathieu ; Ignaszewski, Mark ; Baringer, Molly O. ; Schmid, Claudia ; Lyman, John ; McTaggart, Kristene E. ; Purkey, Sarah G. ; Zilberman, Nathalie ; Alkire, Matthew ; Swift, Dana ; Owens, W. Brechner ; Jayne, Steven R. ; Hersh, Cora ; Robbins, Pelle E. ; West-Mack, Deb ; Bahr, Frank B. ; Yoshida, Sachiko ; Sutton, Philip J. H. ; Cancouët, Romain ; Coatanoan, Christine ; Dobbler, Delphine ; Garcia Juan, Andrea ; Gourrion, Jérôme ; Kolodziejczyk, Nicolas ; Bernard, Vincent ; Bourlès, Bernard ; Claustre, Hervé ; d’Ortenzio, Fabrizio ; Le Reste, Serge ; Le Traon, Pierre-Yves ; Rannou, Jean-Philippe ; Saout-Grit, Carole ; Speich, Sabrina ; Thierry, Virginie ; Verbrugge, Nathalie ; Angel-Benavides, Ingrid M. ; Klein, Birgit ; Notarstefano, Giulio ; Poulain, Pierre Marie ; Vélez-Belchí, Pedro ; Suga, Toshio ; Ando, Kentaro ; Iwasaska, Naoto ; Kobayashi, Taiyo ; Masuda, Shuhei ; Oka, Eitarou ; Sato, Kanako ; Nakamura, Tomoaki ; Sato, Katsunari ; Takatsuki, Yasushi ; Yoshida, Takashi ; Cowley, Rebecca ; Lovell, Jenny L. ; Oke, Peter ; van Wijk, Esmee ; Carse, Fiona ; Donnelly, Matthew ; Gould, W. John ; Gowers, Katie ; King, Brian A. ; Loch, Stephen G. ; Mowat, Mary ; Turton, Jon ; Pattabhi Rama Rao, Eluri ; Ravichandran, M. ; Freeland, Howard ; Gaboury, Isabelle ; Gilbert, Denis ; Greenan, Blair J. W. ; Ouellet, Mathieu ; Ross, Tetjana ; Tran, Anh ; Dong, Mingmei ; Liu, Zenghong ; Xu, Jianping ; Kang, KiRyong ; Jo, HyeongJun ; Kim, Sung-Dae ; Park, Hyuk-Min
    In the past two decades, the Argo Program has collected, processed, and distributed over two million vertical profiles of temperature and salinity from the upper two kilometers of the global ocean. A similar number of subsurface velocity observations near 1,000 dbar have also been collected. This paper recounts the history of the global Argo Program, from its aspiration arising out of the World Ocean Circulation Experiment, to the development and implementation of its instrumentation and telecommunication systems, and the various technical problems encountered. We describe the Argo data system and its quality control procedures, and the gradual changes in the vertical resolution and spatial coverage of Argo data from 1999 to 2019. The accuracies of the float data have been assessed by comparison with high-quality shipboard measurements, and are concluded to be 0.002°C for temperature, 2.4 dbar for pressure, and 0.01 PSS-78 for salinity, after delayed-mode adjustments. Finally, the challenges faced by the vision of an expanding Argo Program beyond 2020 are discussed.
  • Article
    Review of oceanic mesoscale processes in the North Pacific: physical and biogeochemical impacts
    (Elsevier, 2023-02-20) Ueno, Hiromichi ; Bracco, Annalisa ; Barth, John A. ; Budyansky, Maxim V. ; Hasegawa, Daisuke ; Itoh, Sachihiko ; Kim, Sung Yong ; Ladd, Carol ; Lin, Xiaopei ; Park, Young-Gyu ; Prants, Sergey ; Ross, Tetjana ; Rypina, Irina I. ; Sasai, Yoshikazu ; Trusenkova, Olga O. ; Ustinova, Elena I. ; Zhong, Yisen
    Mesoscale eddies impact the marine ecosystem of the North Pacific and its marginal Seas.•Impacts vary with time and regions. Knowns and unknowns are summarized.•How climate change will modify mesoscale processes remains a key open challenge.Physical transport dynamics occurring at the ocean mesoscale (∼20 km – 200 km) largely determine the environment in which biogeochemical processes occur. As a result, understanding and modeling mesoscale transport is crucial for determining the physical modulations of the marine ecosystem. This review synthesizes current knowledge of mesoscale eddies and their impacts on the marine ecosystem across most of the North Pacific and its marginal Seas. The North Pacific domain north of 20°N is divided in four regions, and for each region known, unknowns and known-unknowns are summarized with a focus on physical properties, physical-biogeochemical interactions, and the impacts of climate variability and change on the eddy field and on the marine ecosystem.
  • Article
    OceanGliders: A component of the integrated GOOS
    (Frontiers Media, 2019-10-02) Testor, Pierre ; de Young, Brad ; Rudnick, Daniel L. ; Glenn, Scott ; Hayes, Daniel J. ; Lee, Craig M. ; Pattiaratchi, Charitha ; Hill, Katherine Louise ; Heslop, Emma ; Turpin, Victor ; Alenius, Pekka ; Barrera, Carlos ; Barth, John A. ; Beaird, Nicholas ; Bécu, Guislain ; Bosse, Anthony ; Bourrin, François ; Brearley, J. Alexander ; Chao, Yi ; Chen, Sue ; Chiggiato, Jacopo ; Coppola, Laurent ; Crout, Richard ; Cummings, James A. ; Curry, Beth ; Curry, Ruth G. ; Davis, Richard F. ; Desai, Kruti ; DiMarco, Steven F. ; Edwards, Catherine ; Fielding, Sophie ; Fer, Ilker ; Frajka-Williams, Eleanor ; Gildor, Hezi ; Goni, Gustavo J. ; Gutierrez, Dimitri ; Haugan, Peter M. ; Hebert, David ; Heiderich, Joleen ; Henson, Stephanie A. ; Heywood, Karen J. ; Hogan, Patrick ; Houpert, Loïc ; Huh, Sik ; Inall, Mark E. ; Ishii, Masao ; Ito, Shin-ichi ; Itoh, Sachihiko ; Jan, Sen ; Kaiser, Jan ; Karstensen, Johannes ; Kirkpatrick, Barbara ; Klymak, Jody M. ; Kohut, Josh ; Krahmann, Gerd ; Krug, Marjolaine ; McClatchie, Sam ; Marin, Frédéric ; Mauri, Elena ; Mehra, Avichal ; Meredith, Michael P. ; Meunier, Thomas ; Miles, Travis ; Morell, Julio M. ; Mortier, Laurent ; Nicholson, Sarah ; O'Callaghan, Joanne ; O'Conchubhair, Diarmuid ; Oke, Peter ; Pallás-Sanz, Enric ; Palmer, Matthew D. ; Park, Jong Jin ; Perivoliotis, Leonidas ; Poulain, Pierre Marie ; Perry, Ruth ; Queste, Bastien ; Rainville, Luc ; Rehm, Eric ; Roughan, Moninya ; Rome, Nicholas ; Ross, Tetjana ; Ruiz, Simon ; Saba, Grace ; Schaeffer, Amandine ; Schönau, Martha ; Schroeder, Katrin ; Shimizu, Yugo ; Sloyan, Bernadette M. ; Smeed, David A. ; Snowden, Derrick ; Song, Yumi ; Swart, Sebastiaan ; Tenreiro, Miguel ; Thompson, Andrew ; Tintore, Joaquin ; Todd, Robert E. ; Toro, Cesar ; Venables, Hugh J. ; Wagawa, Taku ; Waterman, Stephanie N. ; Watlington, Roy A. ; Wilson, Doug
    The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.